Robert King Byrd (November 4, 1823 – May 2, 1885) was an American soldier and politician. A Southern Unionist, he commanded the Union Army's First Tennessee Infantry during the Civil War, and saw action at Cumberland Gap, Stones River, and in the Knoxville and Atlanta campaigns. He represented his native Roane County at the pro-Union East Tennessee Convention on the eve of the war in 1861, and at the Nashville convention that reorganized the Tennessee state government toward the end of the war in January 1865.